Micromachined ultrasonic transducers with a slotted membrane structure

Abstract

A piezoelectric micromachined ultrasonic transducer (PMUT) device includes a substrate having an opening therethrough and a membrane attached to the substrate over the opening. A portion of the membrane that overlies the opening is divided into a plurality of cantilevers that are mechanically coupled so that the cantilevers resonate at a common frequency.

Description

CLAIM OF PRIORITY[0001]This application is a continuation of International Patent Application Number PCT / US2015 / 053605 filed Oct. 1, 2015, the entire contents of which are incorporated herein by reference in their entirety.[0002]International Patent Application Number PCT / US2015 / 053605 claims the priority benefit of U.S. Provisional Application No. 62 / 058,909 filed Oct. 2, 2014, the entire contents of which are incorporated herein by reference in their entirety.NOTICE OF MATERIAL SUBJECT TO COPYRIGHT PROTECTION[0003]A portion of the material in this patent document is subject to copyright protection under the copyright laws of the United States and of other countries. The owner of the copyright rights has no objection to the facsimile reproduction by anyone of the patent document or the patent disclosure, as it appears in the United States Patent and Trademark Office publicly available file or records, but otherwise reserves all copyright rights whatsoever. The copyright owner does ...

AI Technical Summary

Benefits of technology

The patent describes a new design for a piezoelectric ultrasonic device that includes a clamped membrane that is partially released by cutting the membrane into cantilevers. This design has several advantages over a fully clamped membrane, including reduced stress sensitivity, increased acoustic sensitivity, and easier adjustment of resonance frequency. This new design has applications in a variety of fields where ultrasonic imaging is used, such as medical diagnosis and non-destructive testing.

Problems solved by technology

Several designs have been suggested to reduce stress sensitivity, such as released cantilevers and flexurally-suspended membranes, but they all show poor acoustic performance and or poor manufacturability (e.g. inefficient resonance modes, cracks created by stress concentrations, poor micro-fabrication yield)

However, for a pMUT operated at resonance, small differences caused by fabrication variations can cause the cantilevers to have slightly different resonance frequencies, resulting in considerable negative impact on the acoustic performance of the device when operated at resonance.

Specifically, when excited at a single frequency, mismatched cantilevers will oscillate with significantly different phase and amplitude, creating phase and amplitude errors in the ultrasound signal.

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